Broadcast receiving circuit and apparatus



Nov. 22, 1949 E. M. CALLENDER 2,439,003

BROADCAST RECEIVING CIRCUIT AND APPARATUS Filed Feb. 12, 1946 2 Sheets-Sheet 1 CALL MICROPHONE AUDIO PLtFIER AND DETECTOR 50mm LEVEL MICROPHONE CONTROL INVENTOR EDWIN M. CALLENDER ATTORNEY Nov. 22, 1949 E. M. CALLENDER 2,489,008 1 BROADCAST RECEIVING CIRCUIT AND APPARATUS Filed Feb. 12, 1946 2 Sheets-Sheet 2 r iOZ 103 QUT PUT 104 iOi v INVENTOR EDWIN M. CALLENDER ATTORNEY INPUT ment.

Patented Nov. 22, 1949 UNITED STATES PATENT i QFF-ICE BROADCAST RECEIVING. CIRCUIT AND APPARATUS Edwin M. Callender, 'Cynwyd, Pa, assignor toThe Budd Company, Philadelphia,- Pa, a corporation of Pennsylvania Application February 12, 1946, Serial.No.-64 7,155

connection with train operation. Difliculty also has developed in vpreventing disturbance of passengers who do not wish to hear a broadcast.

Difficulty also develops in the maintenance of uniformity in the reception independently of whether or not a few or a large number of listeners are utilizing the equipment.

A primary .object of the. invention, therefore, is to provide radio broadcast receptionequipment which may be used by any or all passengers at will and which will be substantially uniform in volume irrespective of the number of listeners.

An object alsois to provide such a system of reception for train service which is audible. only to an individual who desires to utilize the equipcally makes adjustment for variation intrain noises so that the volume of reception remains at a predetermined level above the ground or base noises of the train. An object also.,is .to-

provide a means of chair seat adaptation suitable for passengers on the railway car. Other objects of the invention will become apparent on consideration .of the specific circuits andapparatus as employed in the system and as describedin the following specificationand in the accompanying drawings,in which:

Figure 1 is a diagram of the circuit employed in the system;

Figure 2 is'a detailed diagram of abranch cirtion in relation to the ground noises of the railway car;

Figure} isan. elevation of a car seatequipped with the receiving apparatus of the system;

Figure 4 is. a section through the seat head rest, showing the speaker and Figure 5 is an elevation of the rear sidelof a pair of seats as frequently employed in arailway car,.showing in dotted outline th position of the speakers.

Referring to Figures 3 and 4 of the drawings, there is shown a car seat 1 of the .type suitable for installation in pairs on either. sideof the These seats arecentral aisle ofa railway car.

Still another object of the invention is. to provide a system of reception which automati- 2 single passenger seats and are providedwith a base support .2 on which is ..mounted the seat section .3 ,,and the.. back rest 4 including .the head .rest.5. @Arm rests.-6..are,considered as part of the equipment. Infthe head rest .of. each of these seats there is positioned. aspeaker unit I which is lenclosedrbythe rubber cushioning material I l forming the exterior layers of the head rest, there being tubular openings I2 extending through the rubberized. materialadjacent the point of head .rest to facilitate passage ofsound from the chair interior. A removable rubber panel l3 gives accessto the speakerunit 1. Connections .to the speaker are. made through a conduit 8 to the centerarm restfi, and at the forward end of the .arm resta switch control 9 is. providedby means of. which the passenger may adjust the reception to any one of-a .group of different stations or interrupt thecircuit as desired. The cable from the switch isled down through the base of the chair to a conduit l0 located beneath the floor of the car.

The circuit provided to supply each seat in the car is illustratedin Figure l of the drawing.

For trainreceptlon a'choice of various means may be made as the basis of reception and distribution. For example,.one car of the train may be equipped with a master receiver and amplifying unit, which may be utilized to condition the reception fordistribution to each of the different cars of the train. Alternatively, each car of the train. maybe independently. equipped for reception and amplification. so that irrespective of association with any. other cars it may be operated to .supply complete broadcast reception to the passengers. The description. as follows will cover a. system whichiorms a completeinde- .rpendent unit for individual car reception and distribution of radiobroadcast.

. cuit for controlling the volume of radiorecep- The numeral .l.5 indicates the antenna of the system.which is normally attached to the car ,.roof. This.antenna leads into agroup of sepalijate radio channels'which are applicable to the different stations for .whichsreception is desired, .four bein .Shown' in thedrawingas indicated by thenumerals Iii, ll. 18 and I9. ,Each channel is providedwith the -equipmentior radio detec- A tion and amplificationas indicated by the. conv,Ventionalboxed ,units 20,. 2|, 22 and 23 of the figure. Each channel includes also the usual unit for audio-amplification, as indicated by the numerals .24; 25, 26 and 21. The radio'and audioamplification units oieach channel are connected ,toeether @through switches 28 and-.29. These switches are-intended to control the modification of the reception from broadcast to recorded or local microphone broadcast. In Figure l a tape recorder is indicated by the numeral 3| with connections by circuit 32 to the various audic-amplifiers 24, 25, 26 and 2'! through switch 29. Contacts 33 are provided in the circuit 32 by means of which, and the switches 28, proper connection is made for transmission from the recorder 3|. Similarly, the call microphone unit 34=is connected to a circuit 35 having contacts 35a through which a circuit is established from th microphone by means of switches 29 to the audio-amplifiers 24, 25, 26 and 2?. The transmitted signal, whether it be derived from radio broadcast, recorder or microphone, leads into a series of cables 36, 31, 38 and 39 by means of conductors 40, 4|, 42 and 43. These cables lead to the proper conduits in the wall or underneath the car and possess appropriate taps leading upward beneath the car seats, as shown in Figure 3 of the drawings.

In exemplification of the tapped connection to the cables, there is shown in Figure 1 the branch circuits indicated by conductors 44, 45, 46, 41 and 48. Conductors 44 to 41 are taps on the cables 36 to 39 of the four channels. Conductor 48 constitutes the return grounded circuit which connects with the grounded circuit 49 connecting the cable sheaths to ground. Each of the four conductors 44 to 41 are connected to the manual switch control 9 positioned on a chair arm seat through impedances B, 5], 52 and 53. These conductors at the switch connect to contacts 54, 55, 5B and 51 from which an electrical circuit is established to the return grounded circuit 43 by means of a rotatable disk or drum connector 58 and a connecting conductor 59. The plate 58 is provided with a notch Ell which when aligned to any one of the contacts 54 to 51 serves to disconnect electrically the disk and the contact. At the same time all of the other three contacts are in electrical engagement with the disk, thus establishing a continuous circuit from three of the various channels to the ground circuit. As shown, the contact 54 is disconnected and the contacts 55, 56 and 51 are electrically connected to the associated channel cables.

In conjunction with the circuit as described is a second branch circuit having parallel connections from each of the conductors 44 to 41 through conductors $2, 63, 64 and 65 to the return circuit 48. These conductors include contacts 65, 61, 58 and 65, forming part of a second switch unit including a movable arm which is ganged with the disk 58. Movement of the arm ill from contact to contact brings about simultaneous movement of the disk 58 with its notch 65 in such a manner that when, for example, the contact 55 is closed in circuit by the arm ID, the notch 50 of disk 58 clears the contact 54. eliminating impedance 50 from the associated parallel circuit. The pivot shaft of arm '16 has connection through the transformer element H of a loud speaker unit to the grounded return circuit 48. The value of the impedance of the transformer 'H is approximately that of the impedance 5!! which is cut out by the notch in switch disk 58. The transformer H is part of the loud speaker unit I which, as shown in Figure 3, is in the head rest of the car seat.

It now appears that when the occupant of the seat manipulates the switch 9 so as to bring the movable arm it into engagement with the contact 65, the loud speaker I is placed in circuit while the impedance 5B of the auxiliary circuit is CAD til

cut out. Since the impedance values of these two circuits is approximately the same, the total load on the circuit is not appreciably changed. This maintenance of load continues when the movable arm 30 of the switch is applied to contacts 57, 58 or 55, and since this balance of im'pedances is maintained for the equipment at each car seat, it is apparent that irrespective of the number of listeners the car load for reception remains practically the same. It is, of course, understood that while the switch arrangement as used is applied to two loud speaker units only, as shown in Figure 1, in extension the same equipment is applied to all the various loud speakers of the car.

As described to this point, the circuit of Figure 1 is operative if no requirement exists for automatic adjustment of the volume of reception in accordance with variation in the ground noise of the railway car. It is, of course, recognized that when a railway car is in transit carrying passengers, in addition to the noise of movement due to the car itself on the rails, there is the noise of passenger conversation and. miscellaneous noises incident to occupation of the car which form a ground or base noise level above which the volume of reception must extend in order to be audible to the listener. This room noise is not constant in value but tends to be variable with conditions, being more pronounced during the day-time and being of considerably reduced value in the late hours of the night. Unless adjustment is made for this change in ground noise, what may be adequate volume during the day-time may be excessive volume at night, or what may be adequate volume in a period of lull during the day-time may subsequently during the day be insufficient. In order to adjust the volume automatically to these room noises I have provided in addition to the circuit already described a supplementary circuit indicated by the numeral 15 which is connected generally in parallel with the audio-amplifiers 24 to 27, as shown in Figure l and in detail in Figure 2.

Referring particularly to Figure 2, a pick-up i6 is connected to the car interior where it may readily receive car noises. This pick-up is connected to the cathode and grid of an amplifying tube '11, the output of which passes through the transformer 13 and rectifier i9 and through the capacitor 89 and potentiometer 8|. Resistances B3 of appropriate values are included in' the circuit to smooth out the rectified wave in conjunction with the capacitor 88. The variable contact arm 82 of the potentiometer has connection to the control grid 84 of a pentagrid mixer amplifier 85 through a resistor 85. The number 3 control grid 81 of this tube is connected through a capacitor 83 to the anode of an amplifying tube 89. The cathode and grid of tube 89 have connection respectively to the terminals 90 and 9! of the input circuit corresponding to point 98 and ground {it of the circuit of Figure 1. Control grid 84 of the pentagrid tube is connected to the number 3 grid 8'! through a resistor 92, as shown. Control of the voltage of the control grid 87 is obtained by the circuit from point 93 through resistor 94 to the potentiometer 95 in the grounded cathode circuit of the pentagrid tube. The number 2 and 4 screen grids of the pentagrid tube are connected to a positive source of potential. and to ground through a capacitor, as shown, in the usual way. Further control of the pentagrid is obtained by use of the potentiometer 96 connected to the positive side of the potenegaecrcos tiometer Bl throughc'on'ductor- 91:" The'pentagri'd tube" "circuit includes the anode '98 and cathode" 99 and conductor J connecting the anode-=to thecontrolgridofthapower amplifier tube lol. The anode of this tubehasconnection directly to the amplifier transformer 102," the secondary terminalpoints I 03 I Mgithe'i point il 03 1 corresponding to lines 4E8, GI, 42, 43;: and :pointnlM" correspondingltor the line .104 andtground connected thereto in the generalbir'cuit"of'Figure 1.

In the operation of this so 'called expansion.

circuit: the ground noises ofthe car are: picked upby the --microphone- 16- and amplified i and rectified by the tube 19 to-"form: a.- direct current in the potentiometer -8I.- A-partof this amplified voltage is impressed-upontne'control gridLnum' berl (grid'8'4) of-the-pentagrid tube simultaneously withthe reception-of signals from=the-input terminals Bll-andSI-tothe number 3 control grid-(grid 81). The-tube thus acts as a mixer, and" since the number 1- grid-is of the vari'able mu type;- an expansion involume as-received from the potentiometer 8! of the noise pick-up results in an increased expansion of the volume in the pentagrid tube output which on being amplified is placed in the output channels. Thus the volume of output is automatically increased with increase of ground noise volume, and vice versa. By adjustment of the potentiometer controls BI and 96 the degree of amplification over ground a noises is predetermined.

It now appears from the description as made hereinabove that not only from the viewpoint of variation in number of users, but also from the viewpoint of variation in ground noises within the car itself, uniformity is accomplished and hence the system is thus made useable and effective in railway car uses. It is apparent also that by adjustment of switches 28 and 29 either a phonograph or other record transmission or microphone transmission giving personal directives and the like for information, such as news items, may be made at will without disturbing the setup of the circuits.

By placing the speaker in the center of the car seat head rest the distance from speaker to ear is made short. Combining this short distance of reception with the use of rubber composition chain panels provided with selected tubular openings, the speaker sound is so controlled that for all practical uses only the chair occupant may hear the broadcast. Thus the broadcast may be made available to all who choose to listen without disturbance of those who prefer not to listen.

Modifications of the structure and circuits as described may be made to adapt the same to desired uses. For example, where the chair head rest material is soft it may be desirable to place a rigid protective shield around the speaker. Also, while the volume of all speakers may be readily controlled at the main control point, individual volume controls such as indicated at l IQ and ill may be used for each speaker.

While the system as described has been found useful, obviously changes may be made in the details of circuit connection and association and the installation of apparatus, and hence no limitation is implied other than may be required by the claims hereto appended.

What is claimed is:

1. In a system for signal reception, the combination of receiving and amplifying apparatus, plural main electrical conductors connected to said apparatus for transmission of separate signal'si a return ma'in conductor-for said signaia a speaker; a-"fir'st' group-of electrical branch trans missiom connections *between said speaker: and

eachof said maincenductors; aswitch interposed: in'*-s'aid'-branch-transmission connectionsv havingi: contacts forclosing" anyone or the connections while-"maintaining the 1 other connections open, a: retiirn= branch connection froml the speaker; to; the retii-rn -main conductor; a'azsecond group .of:: connections between saidmain transmissionacon-a ductors-and return branch connection inq aralleh With' the speaker, an impedance positioned in? each -connectionof: said-second group havingfia resistance valueequiva'lent to thatof the speakerand a;#swit'ch interposed in. said second group of v connections having contacts for opening any one of the- 'connections' while maintaining the other 7 connections 'clos'ed whereby on 'closure of any oneof tli 'e fiist grOup o f:connections to the speak er;-the-"corresponding :connection of the second: g roup to aacommon main'transmissionconductor may be opened: andtheiother connections of the-- second groupmlo'seu. 5.

2. In a system for signal reception, the combination of receiving and amplifying apparatus, plural main electrical conductors connected to said apparatus for transmission of separate signals, a return main conductor for said signals, a speaker, a first group of electrical branch transmission connections between said speaker and each of said main conductors, a switch interposed in said branch transmission connections having contacts for closing any one of the connections while maintaining the other connections open, a return branch connection from the speaker to the return main conductor, a second group of connections between said main transmission conductors and return branch connection in parallel with the speaker, an impedance positioned in J each connection of said second group having a resistance value equivalent to that of the speaker, a switch interposed in said second group of connections having contacts for opening any one of the connections while maintaining the other connections closed, and means for moving said switches in unison to close the speaker circuit and open a corresponding parallel impedance circuit to the same main transmission conductor, whereby the circuit load is maintained substantially uniform.

3. In a system for power reception, a combination of an electric transmission conductor, a return conductor, a translating device and first switch connected in series between said conductors, an impedance and second switch connected in series between said conductor and in parallel with said translating device and first switch, said impedance having a value equivalent to that of the translating device, whereby on opening of said first switch, said second switch may be closed to introduce the impedance in the circuit and thereby maintain the load transmitted substantially uniform.

4. In a system for signal reception, a combination of an electric transmission conductor, a return conductor, a speaker and first switch connected in series between said conductors, an impedance and second switch connected in series between said conductor and in parallel with said speaker and first switch, said impedance having a value equivalent to that of the speaker, whereby on opening of said first switch, said second switch may be closed to introduce the impedance in the circuit and thereby maintain-the load.

transmitted substantially uniform.

5. In a system for signal reception, a combination of plural main electrical conductors for transmission of separate signals, a return main conductor for said signals, a translating device, a first group of electrical branch transmission connections, one connection being between said device and each of said main conductors, switching means interposed in said branch transmission connections having contacts for closing any one of the connections while maintaining the other connections open, a return branch connection from the device to the return main conductor, a second group of connections between said main transmission conductors and return branch connection in parallel with the device, an impedance positioned in each connection of said second group having a resistance value equivalent to that of the device, and switch means interposed in said second group of connections having contacts for opening any one of the connections thereof while maintaining the other connections closed, whereby on closure of any one of the first group of connections to the device, the corre- 8 sponding connection of the second group may be opened and the other connections of the second group closed.

EDWIN M. CALLEN'DER.

REFERENCES CITED The following references are of record in the file of this patent: 

